Internal combustion piston engine with an adjustable inflating element

ABSTRACT

An internal combustion piston engine based on a four-stroke process, having a crankcase in which at least one cylinder/piston assembly is arranged, the piston being guided by a connecting rod connected to a crankshaft. At least one cylinder head ( 1 ) closes the cylinder, each of whose intake and exhaust channels are controlled by at least one intake valve and at least one exhaust valve ( 2, 2   a ). The intake and exhaust valves are actuable by a finger lever or a rocker arm driven by a camshaft ( 12 ) through intake and exhaust cams. The finger levers or rocker arms are guided on at least one axle ( 10 ). At least one additional cam is provided in the region of the base circle of the outlet cam for an additional opening of the at least one exhaust valve ( 2, 2   a ), and a control element is installed between the finger lever or rocker arm and the exhaust valve or valves ( 2, 2   a ), which control element can be connected to a pressure oil source and has a variable length, so that the additional cam is active during a compression relief operation and inactive during a pure engine operation. The control element is configured as an inflating element ( 8 ) and is operatively connected through a working piston ( 7 ), with interposition of a spacer, to a bridge ( 4 ) associated to a plurality of exhaust valves ( 2, 2   a ), or is operatively connected to a valve stem of an exhaust valve.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of German Patent Application No. 102010011455.3, filed Mar. 15, 2010, which is incorporated herein by reference as if fully set forth.

FIELD OF THE INVENTION

An internal combustion piston engine based on a four-stroke process, comprising a crankcase in which at least one cylinder/piston assembly is arranged, the piston being guided by a connecting rod connected to a crankshaft, further comprising at least one cylinder head for closing the cylinder, each of whose intake and exhaust channels are controlled by at least one intake valve and one exhaust valve, said intake and exhaust valves being actuable by a finger lever or a rocker arm driven by a camshaft through intake and exhaust cams, the finger levers or rocker arms being guided on at least one axle, further comprising at least one additional cam in the region of the base circle of the outlet cam for an additional opening of at least one exhaust valve, and also comprising a control element that is installed between the finger lever or rocker arm and the exhaust valve or valves, which control element can be connected to a pressurized oil source and whose length is variable, so that the additional cam is active during a compression relief operation and inactive during a pure engine operation.

BACKGROUND OF THE INVENTION

A generic internal combustion piston engine of the pre-cited type is known from U.S. Pat. No. 3,809,033. An actuating piston installed in the rocker arm of this engine is operatively connected to a bridge associated with two exhaust valves. The pressure chamber of the actuating valve is controlled by a control valve, so that oil pressure can be increased and decreased and the actuating piston can be retracted for the performance operation of the internal combustion engine and be extended for the braking operation. The additional cam is active in the one case and inactive in the other. The valve lash is adjusted by means of a screw on the other end of the rocker arm.

A drawback of this configuration is that the oil pressure is used directly for the actuation of the piston, so that a high pressure or a larger piston cross-section is required and strong pressure fluctuations can occur. Moreover, additional measures are required during engine operation in order to avoid vibrations of the transmitting elements resulting from larger lash in the base circle region of the outlet cam. Furthermore, the additional valve lash adjusting screw is considered as a drawback because, irrespective of the additional complexity and expense caused by the thread and the like, it constitutes an undesired additional mass.

Further, an internal combustion piston engine comprising a compression relief device is also known (DE 30 03 566 A1). In this internal combustion engine, the additional cam is configured as a movable component that can be pushed into the base circle contour or pushed outwards out of the base circle contour. For this purpose, the camshaft has a hollow configuration and comprises an actuating device which displaces the additional cam. The actuating device must further also comprise actuating elements outside of the camshaft through which actuating elements the actuating device is controlled. Besides this, the valve lash for the engine operation must be adjusted separately.

The required structural complexity for extending and retracting the additional cams is considerably high and cost-intensive and therefore considered as a drawback.

SUMMARY OF THE INVENTION

It is therefore the object of the invention to improve an internal combustion piston engine with the initially described features, so as to provide an effective engine brake through intermittent opening of one or more exhaust valves in the region of the upper dead center of the internal combustion piston engine, which brake must be realizable through simple measures and low costs. In addition, this should be accomplished in connection with components of a hydraulic lash adjusting element. Moreover, valve lash must be adjustable in a simple manner.

The invention achieves the above object by the fact that the control element is configured as an inflating element and is operatively connected through a working piston, with interposition of a spacer, to a bridge associated to a plurality of exhaust valves, or is operatively connected to a valve stem of an exhaust valve.

By reason of this configuration, only a low pressure is required as a control oil pressure because the inflating element builds up pressure by itself.

Moreover, by the use of spacers configured with graded heights, the valve lash can be adjusted by correspondingly replacing the spacer with another suitable spacer.

It may be pointed out that, in addition to being used as an engine brake in form of a compression relief device the inventive configuration can also be used for internal gas recirculation or for hybridization.

In an advantageous development of the invention, the spacers are configured as ball sockets which are operatively connected to a ball head of a working piston. Through the use of a ball socket and a ball head, undesired surface pressures are avoided. Moreover, ball sockets possess the advantage that they can be fixed safe against loss on the ball head of the working piston of the inflating element, and the bridge or the valve stem does not require any additional receptions.

According to a further proposition of the invention, the inflating element comprises the components of a hydraulic valve lash adjusting element (HVA) such as working piston, housing, resetting spring, piston and non-return valve on the piston, a control piston being additionally provided and loaded on one side by a spring and on the other side by pressure oil, and the control piston is operatively connected to the valve body of the non-return valve in opening direction.

When the control piston is loaded with reduced oil pressure, the spring presses the control piston against the valve body of the non-return valve, which is preferably configured as a ball, and opens this. As a result, the control element can get shortened, so that the additional cam is inactive and no compression relief opening of the exhaust valve or valves takes place. The non-return valve, however, still remains active so that no uncontrolled lash is produced in the region of the base circle of the exhaust valve and no uncontrolled vibrations of the transmitting elements occur. The finger lever or rocker arm, if necessary also an installed tappet, is therefore in constant contact with the additional cam. The additional lift, however, is suppressed in this case by the inflating element.

When the control piston is loaded through oil pressure, the non-return valve can close and a pressure is built up in the high pressure chamber between housing, working piston and piston. The thus configured high pressure chamber causes the activation of the additional cam which leads to a switching-on of the compression relief device, the gas recirculation device or a hybridization device.

BRIEF DESCRIPTION OF THE DRAWINGS

For a further elucidation of the invention reference will be made to the appended drawings in which one example of embodiment is shown in simplified illustrations. The figures show:

FIG. 1: a side view of a valve train including a partial section through a cylinder head, a camshaft, an axle for the rocker arm and a bridge, and

FIG. 2: a section through the end of a rocker arm, an inflating element and a bridge.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In FIGS. 1 and 2 a cylinder head of an internal combustion piston engine, as far as specifically shown, is identified at 1. The exhaust channels of the engine are controlled by two exhaust valves 2 and 2 a that are guided in the cylinder head 1 and biased in closing direction by valve springs 3 and 3 a. A bridge 4 is associated to the valve stems of the exhaust valves 2 and 2 a and engages around the ends of the valve stems while being operatively connected to a ball socket 5 supported on a ball head 6 of a working piston 7 which is a component part of an inflating element generally identified at 8. The inflating element 8 is installed in a recess of a rocker arm 9 and supplied with oil from an oil bore in the rocker arm 9, not specifically shown. The rocker arm 9 is mounted on an axle 10 comprising oil channels 11 and 11 a which are connected to the oil circulation of the internal combustion piston engine. The oil pressure delivered to the inflating element 8 can be varied through a control valve, not illustrated. The rocker arm 9 is operatively connected through its other end, not specifically shown, to an exhaust cam of a camshaft 12, preferably through a roller. In the base circle region, the exhaust cam comprises at least one additional cam, separately from the exhaust valve lobes, for an additional opening of the exhaust valves in correspondence with the operation of the internal combustion engine. The inflating element 8 comprises a housing 13 that is inserted into the rocker arm 9 and guides the working piston. The housing 13 and the working piston 7 define a pressure chamber that is controlled by a non-return valve 14 which is arranged on a piston 15. A resetting spring 16 is installed between the piston 15 and the working piston 7 and biases the working piston in direction of the ball head 6. The stroke of the working piston 7 is limited, so that the pressure chamber cannot expand indefinitely even after pressure build-up. The piston 15 and the non-return valve 16 are adjoined by a control piston 17 that is biased by a spring 18 in direction of the piston 15, which spring 18 is supported on the housing 13. In the region between the control valve 17 and the piston 15, the housing 13 comprises a bore 19 that can be supplied with pressure oil through an intermediate space between the housing 13 and the rocker arm 9. The installation space of the spring 18 communicates with the surrounding pressure through a vent bore, so that a pressure build-up is avoided.

The mounting points between the bridge 4 and the ball socket 5 and between the ball socket 5 and the ball head 6 are supplied with oil for lubrication through a central bore 20 in the working piston 7.

LIST OF REFERENCES

1 Cylinder head

2, 2 a Exhaust valves

3, 3 a Valve springs

4 Bridge

5 Ball socket

6 Ball head

7 Working piston

8 Inflating element

9 Rocker arm

10 Axle

11, 11 a Oil channels

12 Camshaft

13 Housing

14 Non-return valve

15 Piston

16 Resetting spring

17 Control piston

18 Spring

19 Bore

20 Oil bore 

1. An internal combustion piston engine based on a four-stroke process, comprising a crankcase in which at least one cylinder/piston assembly is arranged, the piston being guided by a connecting rod connected to a crankshaft, further comprising at least one cylinder head for closing the cylinder, intake and exhaust channels for each of the cylinders are controlled by at least one intake valve and at least one exhaust valve, said intake and exhaust valves being actuable by a finger lever or a rocker arm driven by a camshaft through intake and exhaust cams, the finger levers or rocker arms being guided on at least one axle, at least one additional cam in a region of a base circle of the exhaust cam for an additional opening of the at least one exhaust valve, and a control element is installed between the finger lever or rocker arm and the at least one exhaust valve, the control element is connectable to a pressurized oil source and has a length that is variable, so that the additional cam is active during a compression relief operation and inactive during a pure engine operation, the control element is configured as an inflating element and is operatively connected through a working piston, with interposition of a spacer, to a bridge associated with a plurality of the exhaust valves, or is operatively connected to a valve stem of the exhaust valve.
 2. An internal combustion piston engine according to claim 1, wherein a valve lash is adjusted by using spacers configured with graded heights.
 3. An internal combustion piston engine according to claim 2, wherein the spacers are configured as ball sockets which are operatively connected to a ball head of the working piston.
 4. An internal combustion piston engine according to claim 1, wherein the inflating element comprises components of a hydraulic valve lash adjusting element including a working piston, a housing, a resetting spring, a piston and a non-return valve on the piston, and that a control piston is additionally provided and loaded on one side by a spring and on another side by pressure oil, wherein the control piston can be operatively connected to the valve body of the non-return valve in an opening direction. 